There are many techniques in use to attempt to prevent unauthorized automobile use or theft. These techniques range from simple kill switches to elaborate computer controlled alarm and disabling systems. However, professional thieves study to be proficient at defeating the entire range of anti-theft techniques.
The simplest forms are the easiest to defeat. Keys can be reproduced and locks can be picked, or the thief can hot-wire the ignition system. If a hidden kill switch has been installed, it can also be located and easily bypassed. Hidden kill switches do not usually remain hidden long, due to mechanics and other users of the vehicle being told of the secret location.
At one time audible alarm systems were effective deterrents. This is no longer true because most people are conditioned to false alarms and simply ignore the audible alarms. Thieves recognize this and are no longer deterred. They know how to defeat the audible alarm before anyone becomes concerned. This type of system is only effective when the vehicle owner personally hears the alarm.
Vehicle disabling systems, such as fuel cutoff valves or ignition shut down circuits, are better alternatives. A professional thief can, however, defeat these types of systems. Most of these systems are very repeatable, and therefore become obvious to the thief. Once a thief is aware of the system, he can take appropriate action to defeat it.
Most theft deterrent systems have limited effectiveness. They are usually detectable and defeatable by a proficient thief. To be effective, a proper problem simulation system should be undetectable by the thief. It would appear to be a typical automotive problem, possessing related symptoms that recur unpredictably. It should also employ multiple symptoms related to a specific problem in a random fashion with each symptom having an associated probability of taking place. Each of the random symptoms should exist for some random duration of time before the next symptom, if any can occur.